Invasive Plant

Scotch Thistle

Onopordum acanthium

About This Species

Scotch thistle is a biennial or perennial that reproduces through thousands of seeds that can survive in the soil for over 30 years. The seeds need moisture to germinate. Seeds can spread with the wind, but also in hay and water, and by attaching to clothing or animal fur. It creates dense stands that are extremely difficult for humans and animals to walk through.

How to Identify

Scotch thistle can grow up to 3 m tall and has large pink, purple or sometimes reddish flowers. The stems have spine-edged wings that run up the sides. Leaves are irregularly lobed, have sharp yellow spikes, and are covered in woolly hairs that give the foliage a grey-green appearance.

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